In contrast to rock critics who tend to be sophisticated and complex to a fault, the chroniclers of country music are boosters and appreciators. Especially Doug Green, historian of the Country Music Foundation, writing about the down-home sound of Nashville's rhinestone cowboys. More than Paul Hemphill (The Nashville Sound, 1970) or Steve Price (Take Me Home, 1974), Green writes with devotion--perhaps because the fierce loyalty of Opry fans is infectious. He recognizes that Country, seemingly the most simple and straightforward sound going, is actually a hybrid of many regional styles and musical impulses. One by one he takes the old Appalachian ballads and fiddle tunes of the Carter family; the lonesome yodels of bluesmen like Jimmy Rodgers; the Country swing of Bob Wills and his Texas Playboys; bluegrass and Bill Monroe; the gospel influence; the Cajun yowls of the Louisiana bayou; the rockabilly of Elvis, Carl Perkins, and Jerry Lee Lewis. But the earthy, funky feel of those songs of hard liquor and easy women, fundamentalist religion and abrupt violence and bone-weary work is somehow lost in this smooth, polished narrative. The rough edges aren't there, the sentimentality and bathos aren't there; it's all a bit flat. But an extensive discography and 200 photos should carry it home to the less demanding part of Country's swelling audience.